1. Field of the Invention
The invention relates to inducing a shape change in a cornea for treating a keratoconus condition, or correcting a refractive error or a high order aberration, or combinations thereof, and particularly to generating an intrastromal pocket within a patient's eye and filling with a polymeric insert.
2. Description of the Related Art
Keratoconus is an eye condition that involves bulging of the cornea usually associated with local thinning of the cornea. It is difficult to treat. Most treatments provide temporary solutions that do not result in high quality vision. Hard contact lenses or Rigid Gas Permeable (RGP) lenses may be used to “cover” over the cone of the eye. However, this can result in high distortion and does not achieve optimal vision. Rubbing of the lens on the cone often leads to thinning of the cornea, cornea melt, or other worsening conditions. Laser ablation may be tried for shaving off a protrusion. This cuts against the common sense notion that further thinning would likely lead to worsening conditions. “Intacs”, which are thin strips of plastic (PMMA), may be inserted inside the cornea to attain a less distorted eye. By trial and error, the method may have occasional success, but is unlikely to produce reliable results. It is desired to have a method of corneal surgery that can treat Keratoconus and/or can restore a quality of vision that existed prior to the onset of the Keratoconus condition.
With the advent of wavefront technology, one can now measure minute amounts of ocular aberrations. In fact, none of the current refractive surgery methods, such as Laser In situ Keratomileusis (LASIK), Laser Epitheial Keratomileusis (LASEK), Conductive Kerotoplasty (CK), or Refractive lens exchange, have the ability to modify the eye to achieve the level of accuracy of that of a wavefront aberrometer. Some underlying issues with current refractive surgeries include inaccuracies in surgical methods that induce more optical distortions than they reduce, and traumatic aspects of procedures that induce aggressive healing that negates intended results of the surgery, and can cause vision instability during a healing period.
Currently, the most practiced refractive surgery is LASIK, which involves the creation of a flap, a thin layer of cornea tissue excised by a microkeratome. That procedure often introduces complications such as buttonhole, loss of flap, incomplete flap, and/or epithelium cell ingrowths. The cornea is structurally weakened by LASIK, and cases of estasia have been found in many LASIK patients. Hence, it is desired to provide a refractive surgery method that is safer than LASIK, is less traumatic, provides quicker vision recovery, and/or is reversible.
Techniques of customized ocular aberration correction that cancel aberrations of an individual eye by incorporating wavefront correction in a spectacle lens are described in US patent applications 20030003295A1, 20030143391A1, and 20030143391A1, and in U.S. Pat. No. 6,813,082, which are hereby incorporated by reference. However, these involve careful alignment of the spatial profile of wavefront correction on the eyeglasses with that of the eye in order to achieve maximum benefit. Eyes tend to move at various glaze angles, resulting in a limited usefulness if a maximal cancellation of wavefront aberrations is desired at all times, including when the eye moves to the various glaze angles.
Recently, Advanced Medical Optics introduced Technis, which is an intraocular lens that incorporates a fixed amount of spherical aberration correction. However, the same amount of correction does not provide optimal correction for every eye. Because it is not customized for each patient, the benefit may therefore be limited.